Propylene-based polymer compositions for injection molding

ABSTRACT

The present invention is related to a propylene-based injection molded composition made from a polymer blend comprising from 45 to 85 wt % of a polymer blend modifier having a weight average molecular weight of 10,000 to 100,000 g/mole and from 15 to 55 wt % of a propylene-based elastomer having a weight average molecular weight of from 100,000 to 300,000 g/mole, where the weight percent of the polymer blend modifier and the propylene-based elastomer are based on the total weight of the polymer blend. The polymer blend modifier comprises a first propylene-based polymer and a second propylene-based polymer, where the first and second propylene-based polymers are different and are individually selected from a homopolymer of propylene or a copolymer of propylene and ethylene or a C 4  to C 10  alpha-olefin.

PRIORITY CLAIM

This application is a 371 National Phase Application of PCT ApplicationSerial No. PCT/CN2015/000209 filed Mar. 27, 2015, which is incorporatedherein by reference in its entirety.

FIELD OF INVENTION

The invention relates to a propylene-based composition for use ininjection molding applications.

BACKGROUND

Polyolefin-based polymers, such as propylene-based polymers, arecustomarily provided in a molten form into a plunger-type apparatus toproduce an injection molded article. The process generally includes thesteps of adjusting a mold, filling a mold with a molten polyolefin-basedpolymer or other injection material, and cooling the article constructedtherefrom. The injection molding process is known in the art and is usedto construct a variety of plastic-based articles, e.g., packagingmaterials, automobile parts, furniture, stationery, and toiletries.Injection molded articles sought are those that provide a desired levelof toughness without requiring a lengthy manufacturing time, effected bythe processability and crystallization characteristics of the feedpolyolefin material.

Many different types of polymers are known and have been used ininjection molding formulations. Exemplary polyolefin-based polymers andmethods of making polymer compositions are disclosed in U.S. Pat. Nos.7,294,681 and 7,524,910. WO Publication No. 2013/134038 discloses amethod for producing a polymer blend having at least two differentpropylene-based polymers produced in parallel reactors. The multi-modalpolymer blend has an Mw of about 10,000 g/mol to about 150,000 g/mol.

However, there remains a need for a propylene-based formulation for usein an injection molding application that have good flow properties andcrystallization characteristics, as compared to molding formulationsthat are currently available. The foregoing and/or other challenges areaddressed by the methods and products disclosed herein.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows processability parameters for polymer blends for use asinjection molding articles.

FIG. 2 shows crystallization rate for polymer blends for use asinjection molding articles.

FIG. 3 shows crystallization time for polymer blends for use asinjection molding articles.

SUMMARY

In one aspect, a polymer blend is provided for use in an injectionmolded composition. The polymer blend is made from 45 to 85 wt % of apolymer blend modifier based on the weight of the polymer blend and from15 to 55 wt % of a propylene-based elastomer based on the weight of thepolymer blend. The polymer blend modifier comprises a firstpropylene-based polymer, a homopolymer of propylene or a copolymer ofpropylene and ethylene or a C₄ to C₁₀ alpha-olefin, and a secondpropylene-based polymer, a homopolymer of propylene or a copolymer ofpropylene and ethylene or a C₄ to C₁₀ alpha-olefin. The secondpropylene-based polymer is different than the first propylene-basedpolymer. The polymer blend modifier has a weight average molecularweight of 10,000 to 100,000 g/mole. The propylene-based elastomer has aweight average molecular weight of 100,000 to 300,000 g/mole.

DETAILED DESCRIPTION

Various specific embodiments of the invention will now be described,including preferred embodiments and definitions that are adopted hereinfor purposes of understanding the claimed invention. While theillustrative embodiments have been described with particularity, it willbe understood that various other modifications will be apparent to andcan be readily made by those skilled in the art without departing fromthe spirit and scope of the invention. For determining infringement, thescope of the “invention” will refer to any one or more of the appendedclaims, including their equivalents and elements or limitations that areequivalent to those that are recited.

The inventors have discovered that propylene-based polymers that have alow molecular weight, such as the propylene based modifiers describedherein, can be advantageously used in injection molding formulations andprovide the resulting polymer blend with good flow properties andcrystallization characteristics. It is believed that these benefits areobtained without compromising toughness properties of the resultinginjection molded articles that is often seen in articles made withformulations containing higher-molecular weight polyolefin polymers.

As used herein, the term “copolymer” is meant to include polymers havingtwo or more monomers, optionally, with other monomers, and may refer tointerpolymers, terpolymers, etc. The term “polymer” as used hereinincludes, but is not limited to, homopolymers, copolymers, terpolymers,etc., and alloys and blends thereof. The term “polymer” as used hereinalso includes impact, block, graft, random, and alternating copolymers.The term “polymer” shall further include all possible geometricalconfigurations unless otherwise specifically stated. Such configurationsmay include isotactic, syndiotactic and random symmetries. The term“blend” as used herein refers to a mixture of two or more polymers. Theterm “elastomer” shall mean any polymer exhibiting some degree ofelasticity, where elasticity is the ability of a material that has beendeformed by a force (such as by stretching) to return at least partiallyto its original dimensions once the force has been removed.

“Propylene-based” as used herein, is meant to include any polymercomprising propylene, either alone or in combination with one or morecomonomers, in which propylene is the major component (i.e., greaterthan 50 mol % propylene).

The term “monomer” or “comonomer,” as used herein, can refer to themonomer used to form the polymer, i.e., the unreacted chemical compoundin the form prior to polymerization, and can also refer to the monomerafter it has been incorporated into the polymer, also referred to hereinas a “[monomer]-derived unit”. Different monomers are discussed herein,including propylene monomers, ethylene monomers, and diene monomers.

“Reactor blend,” as used herein, means a highly dispersed andmechanically inseparable blend of two or more polymers produced in situas the result of sequential or parallel polymerization of one or moremonomers with the formation of one polymer in the presence of another,or by solution blending polymers made separately in parallel reactors.Reactor blends may be produced in a single reactor, a series ofreactors, or parallel reactors and are reactor grade blends. Reactorblends may be produced by any polymerization method, including batch,semi-continuous, or continuous systems. Particularly excluded from“reactor blend” polymers are blends of two or more polymers in which thepolymers are blended ex situ, such as by physically or mechanicallyblending in a mixer, extruder, or other similar device.

The polymers described herein, including the polymer blend modifier andthe propylene-based elastomer, may be prepared using one or morecatalyst systems. As used herein, a “catalyst system” comprises at leasta transition metal compound, also referred to as catalyst precursor, andan activator. Contacting the transition metal compound (catalystprecursor) and the activator in solution upstream of the polymerizationreactor or in the polymerization reactor of the process described aboveyields the catalytically active component (catalyst) of the catalystsystem. Any given transition metal compound or catalyst precursor canyield a catalytically active component (catalyst) with variousactivators, affording a wide array of catalysts deployable in theprocesses described herein. Catalyst systems useful in the processesdescribed herein comprise at least one transition metal compound and atleast one activator. However, catalyst systems of the current disclosuremay also comprise more than one transition metal compound in combinationwith one or more activators. Such catalyst systems may optionallyinclude impurity scavengers. The triad tacticity and tacticity index ofthe polymer may be controlled by the catalyst, which influences thestereoregularity of propylene placement, the polymerization temperature,according to which stereoregularity can be reduced by increasing thetemperature, and by the type and amount of a comonomer, which tends toreduce the length of crystalline propylene derived sequences.

Polymer Blend Modifiers

The Polymer Blend Modifiers (“PBMs”) useful for making the polymer blendfor use in the injection molding article of the invention comprise afirst propylene-based polymer, wherein the first propylene-based polymeris a homopolymer of propylene or a copolymer of propylene and ethyleneor a C₄ to C₁₀ alpha-olefin; and a second propylene-based polymer,wherein the second propylene-based polymer is a homopolymer of propyleneor comprises a comonomer of ethylene or a C₄ to C₁₀ alpha-olefin;wherein the second propylene-based polymer is compositionally differentthan the first propylene-based polymer.

In an embodiment, the PBM has a melt viscosity, measured at 190° C.within the range of from about 800 or 1,000 or 5,000 cP to about 10,000or 15,000 cP. In an embodiment, the PBM has a Melt Flow Rate (“MFR”,230° C./2.16 kg) within the range of from about 1,000 or 2,000 g/10 minto about 5,000 or 10,000 g/10 min. The polymer blend modifier has aweight average molecular weight of 10,000 or 25,000 or 50,000 to 75,000or 100,000 g/mole.

Methods of Preparing PBMs

A solution polymerization process for preparing a PBM is generallyperformed by a system that includes a first reactor, a second reactor inparallel with the first reactor, a liquid-phase separator, adevolatilizing vessel, and a pelletizer. The first reactor and secondreactor may be, for example, continuously stirred-tank reactors.

The first reactor may receive a first monomer feed, a second monomerfeed, and a catalyst feed. The first reactor may also receive feeds of asolvent and an activator. The solvent and/or the activator feed may becombined with any of the first monomer feed, the second monomer feed, orcatalyst feed or the solvent and activator may be supplied to thereactor in separate feed streams. A first polymer is produced in thefirst reactor and is evacuated from the first reactor via a firstproduct stream. The first product stream comprises the firstpropylene-based polymer, solvent, and any unreacted monomer. A similarprocess may be used to produce a second product stream comprising thesecond propylene-based polymer, solvent, and any unreacted monomer.

In any embodiment, the first monomer in the first monomer feed may bepropylene and the second monomer in the second monomer feed may beethylene or a C₄ to C₁₀ olefin. In any embodiment, the second monomermay be ethylene, butene, hexene, and octene. Generally, the choice ofmonomers and relative amounts of chosen monomers employed in the processdepends on the desired properties of the first polymer and final PBM. Inany embodiment, the relative amounts of propylene and comonomer suppliedto the first reactor may be designed to produce a polymer that ispredominantly propylene, i.e., a polymer that is more than 50 mol %propylene. In another embodiment, the first reactor may produce ahomopolymer of propylene.

The second propylene-based polymer is different than the firstpropylene-based polymer. The difference may be measured, for example, bythe comonomer content, heat of fusion, crystallinity, branching index,weight average molecular weight, and/or polydispersity of the twopolymers. In any embodiment, the second propylene-based polymer maycomprise a different comonomer than the first propylene-based polymer orone polymer may be a homopolymer of propylene and the other polymer maycomprise a copolymer of propylene and ethylene or a C₄ to C₁₀ olefin.For example, the first propylene-based polymer may comprise apropylene-ethylene copolymer and the second propylene-based polymer maycomprise a propylene-hexene copolymer. In any embodiment, the secondpropylene-based polymer may have a different weight average molecularweight (Mw) than the first propylene-based polymer and/or a differentmelt viscosity than the first propylene-based polymer. Furthermore, inany embodiment, the second propylene-based polymer may have a differentcrystallinity and/or heat of fusion than the first propylene-basedpolymer.

It should be appreciated that any number of additional reactors may beemployed to produce other polymers that may be integrated with (e.g.,grafted) or blended with the first and second polymers. Furtherdescription of exemplary methods for polymerizing the polymers describedherein may be found in U.S. Pat. No. 6,881,800, which is incorporated byreference herein.

The first product stream and second product stream may be combined toproduce a blend stream. For example, the first product stream and secondproduct stream may supply the first and second polymer to a mixingvessel, such as a mixing tank with an agitator.

The blend stream may be fed to a liquid-phase separation vessel toproduce a polymer rich phase and a polymer lean phase. The polymer leanphase may comprise the solvent and be substantially free of polymer. Atleast a portion of the polymer lean phase may be evacuated from theliquid-phase separation vessel via a solvent recirculation stream. Thesolvent recirculation stream may further include unreacted monomer. Atleast a portion of the polymer rich phase may be evacuated from theliquid-phase separation vessel via a polymer rich stream.

In any embodiment, the liquid-phase separation vessel may operate on theprinciple of Lower Critical Solution Temperature (LCST) phaseseparation. This technique uses the thermodynamic principle of spinodaldecomposition to generate two liquid phases; one substantially free ofpolymer and the other containing the dissolved polymer at a higherconcentration than the single liquid feed to the liquid-phase separationvessel.

Employing a liquid-phase separation vessel that utilizes spinodaldecomposition to achieve the formation of two liquid phases may be aneffective method for separating solvent from multi-modal polymer PBMs,particularly in cases in which one of the polymers of the PBM has aweight average molecular weight less than 100,000 g/mol, and even moreparticularly between 10,000 g/mol and 60,000 g/mol. The concentration ofpolymer in the polymer lean phase may be further reduced by catalystselection.

Upon exiting the liquid-phase separation vessel, the polymer rich streammay then be fed to a devolatilizing vessel for further polymer recovery.In any embodiment, the polymer rich stream may also be fed to a lowpressure separator before being fed to the inlet of the devolatilizingvessel. While in the vessel, the polymer composition may be subjected toa vacuum in the vessel such that at least a portion of the solvent isremoved from the polymer composition and the temperature of the polymercomposition is reduced, thereby forming a second polymer compositioncomprising the PBM and having a lower solvent content and a lowertemperature than the polymer composition as the polymer composition isintroduced into the vessel. The polymer composition may then bedischarged from the outlet of the vessel via a discharge stream.

The cooled discharge stream may then be fed to a pelletizer where thePBM is then discharged through a pelletization die as formed pellets.Pelletization of the polymer may be by an underwater, hot face, strand,water ring, or other similar pelletizer. Preferably an underwaterpelletizer is used, but other equivalent pelletizing units known tothose skilled in the art may also be used. General techniques forunderwater pelletizing are known to those of ordinary skill in the art.

Exemplary methods for producing useful PBMs are further described inInternational Publication No. 2013/134038, which is incorporated hereinin its entirety. In particular, the catalyst systems used for producingsemi-crystalline polymers of the PBM may comprise a metallocene compoundand activator such as those described in International Publication No.2013/134038. Exemplary catalysts may include dimethylsilylbis(2-methyl-4-phenylindenyl) zirconium dichloride, dimethylsilylbis(2-methyl-5-phenylindenyl) hafnium dichloride, dimethylsilylbis(2-methyl-4-phenylindenyl) zirconium dimethyl, and dimethylsilylbis(2-methyl-4-phenylindenyl) hafnium dimethyl.

Polymers of the PBMs

As described herein, the PBM comprises a first propylene-based polymerand a second propylene-based polymer. Preferred first and/or secondpropylene-based polymers of the PBM are semi-crystalline propylene-basedpolymers. In any embodiment, the polymers may have a relatively lowmolecular weight, preferably about 100,000 g/mol or less. In anyembodiment, the polymer may comprise a comonomer selected from the groupconsisting of ethylene and linear or branched C₄ to C₂₀ olefins anddiolefins. In any embodiment, the comonomer may be ethylene or a C₄ toC₁₀ olefin.

In any embodiment, one or more polymers of the PBM may comprise one ormore propylene-based polymers, which comprise propylene and from about 5mol % to about 30 mol % of one or more comonomers selected from C₂ andC₄-C₁₀ α-olefins. In any embodiment, the α-olefin comonomer units mayderive from ethylene, butene, pentene, hexene, 4-methyl-1-pentene,octene, or decene. The embodiments described below are discussed withreference to ethylene and hexene as the α-olefin comonomer, but theembodiments are equally applicable to other copolymers with otherα-olefin comonomers.

In any embodiment, the one or more polymers of the PBM may include atleast about 5 mol %, at least about 6 mol %, at least about 7 mol %, orat least about 8 mol %, or at least about 10 mol %, or at least about 12mol % ethylene-derived or hexene-derived units. In those or otherembodiments, the copolymers may include up to about 30 mol %, or up toabout 25 mol %, or up to about 22 mol %, or up to about 20 mol %, or upto about 19 mol %, or up to about 18 mol %, or up to about 17 mol %ethylene-derived or hexene-derived units, where the percentage by moleis based upon the total moles of the propylene-derived and α-olefinderived units. Stated another way, the propylene-based polymer mayinclude at least about 70 mol %, or at least about 75 mol %, or at leastabout 80 mol %, or at least about 81 mol % propylene-derived units, orat least about 82 mol % propylene-derived units, or at least about 83mol % propylene-derived units; and in these or other embodiments, thecopolymers may include up to about 95 mol %, or up to about 94 mol %, orup to about 93 mol %, or up to about 92 mol %, or up to about 90 mol %,or up to about 88 mol % propylene-derived units, where the percentage bymole is based upon the total moles of the propylene-derived andalpha-olefin derived units. In any embodiment, the propylene-basedpolymer may comprise from about 5 mol % to about 25 mol %ethylene-derived or hexene-derived units, or from about 8 mol % to about20 mol % ethylene-derived or hexene-derived units, or from about 12 mol% to about 18 mol % ethylene-derived or hexene-derived units.

The one or more polymers of the PBM of one or more embodiments arecharacterized by a melting point (Tm), which can be determined bydifferential scanning calorimetry (DSC). For purposes herein, themaximum of the highest temperature peak is considered to be the meltingpoint of the polymer. A “peak” in this context is defined as a change inthe general slope of the DSC curve (heat flow versus temperature) frompositive to negative, forming a maximum without a shift in the baselinewhere the DSC curve is plotted so that an endothermic reaction would beshown with a positive peak.

In any embodiment, the Tm of the one or more polymers of the PBM (asdetermined by DSC) may be less than about 130° C., or less than about120° C., or less than about 115° C., or less than about 110° C., or lessthan about 100° C., or less than about 90° C. In any embodiment, the Tmof the one or more polymers of the PBM may be greater than about 25° C.,or greater than about 30° C., or greater than about 35° C., or greaterthan about 40° C. Tm of the one or more polymers of the PBM can bedetermined by taking 5 to 10 mg of a sample of the one or more polymers,equilibrating a DSC Standard Cell FC at −90° C., ramping the temperatureat a rate of 10° C. per minute up to 200° C., maintaining thetemperature for 5 minutes, lowering the temperature at a rate of 10° C.per minute to −90° C., ramping the temperature at a rate of 10° C. perminute up to 200° C., maintaining the temperature for 5 minutes, andrecording the temperature as Tm.

In one or more embodiments, the crystallization temperature (Tc) of theone or more polymers of the PBM (as determined by DSC) is less thanabout 100° C., or less than about 90° C., or less than about 80° C., orless than about 70° C., or less than about 60° C., or less than about50° C., or less than about 40° C., or less than about 30° C., or lessthan about 20° C., or less than about 10° C. In the same or otherembodiments, the Tc of the polymer is greater than about 0° C., orgreater than about 5° C., or greater than about 10° C., or greater thanabout 15° C., or greater than about 20° C. In any embodiment, the Tclower limit of the polymer may be 0° C., 5° C., 10° C., 20° C., 30° C.,40° C., 50° C., 60° C., and 70° C.; and the Tc upper limit temperaturemay be 120° C., 110° C., 100° C., 90° C., 80° C., 70° C., 60° C., 50°C., 40° C., 30° C., 25° C., and 20° C. with ranges from any lower limitto any upper limit being contemplated. Tc of the PBM can be determinedby taking 5 to 10 mg of a sample of the polymer blend, equilibrating aDSC Standard Cell FC at −90° C., ramping the temperature at a rate of10° C. per minute up to 200° C., maintaining the temperature for 5minutes, lowering the temperature at a rate of 10° C. per minute to −90°C., and recording the temperature as Tc.

The polymers suitable for in the PBM are said to be “semi-crystalline,”meaning that in general they have a relatively low crystallinity. Theterm “crystalline” as used herein broadly characterizes those polymersthat possess a high degree of both inter and intra molecular order, andwhich preferably melt higher than 110° C., more preferably higher than115° C., and most preferably above 130° C. A polymer possessing a highinter and intra molecular order is said to have a “high” level ofcrystallinity, while a polymer possessing a low inter and intramolecular order is said to have a “low” level of crystallinity.Crystallinity of a polymer can be expressed quantitatively, e.g., interms of percent crystallinity, usually with respect to some referenceor benchmark crystallinity. As used herein, crystallinity is measuredwith respect to isotactic polypropylene homopolymer. Preferably, heat offusion is used to determine crystallinity. Thus, for example, assumingthe heat of fusion for a highly crystalline polypropylene homopolymer is190 J/g, a semi-crystalline propylene copolymer having a heat of fusionof 95 J/g will have a crystallinity of 50%. The term “crystallizable” asused herein refers to those polymers which can crystallize uponstretching or annealing. Thus, in certain specific embodiments, thesemi-crystalline polymer may be crystallizable. The semi-crystallinepolymers used in specific embodiments preferably have a crystallinity offrom 2% to 65% of the crystallinity of isotactic polypropylene. Infurther embodiments, the semi-crystalline polymers may have acrystallinity of from about 3% to about 40%, or from about 4% to about30%, or from about 5% to about 25% of the crystallinity of isotacticpolypropylene.

The semi-crystalline polymer of the PBM can have a level of isotacticityexpressed as percentage of isotactic triads (three consecutive propyleneunits), as measured by ¹³C NMR, of 75 mol % or greater, 80 mol % orgreater, 85 mol % or greater, 90 mol % or greater, 92 mol % or greater,95 mol % or greater, or 97 mol % or greater. In one or more embodiments,the triad tacticity may range from about 75 mol % to about 99 mol %, orfrom about 80 mol % to about 99 mol %, or from about 85 mol % to about99 mol %, or from about 90 mol % to about 99 mol %, or from about 90 mol% to about 97 mol %, or from about 80 mol % to about 97 mol %. Triadtacticity is determined by the methods described in U.S. PatentApplication Publication No. 2004/0236042.

The semi-crystalline polymer of the PBM may have a tacticity index m/rranging from a lower limit of 4, or 6 to an upper limit of 10, or 20, or25. The tacticity index, expressed herein as “m/r”, is determined by ¹³Cnuclear magnetic resonance (“NMR”). The tacticity index m/r iscalculated as defined by H. N. Cheng in Macromolecules, 17, 1950 (1984),incorporated herein by reference. The designation “m” or “r” describesthe stereochemistry of pairs of contiguous propylene groups, “m”referring to meso and “r” to racemic. An m/r ratio of 1.0 generallydescribes an atactic polymer, and as the m/r ratio approaches zero, thepolymer is increasingly more syndiotactic. The polymer is increasinglyisotactic as the m/r ratio increases above 1.0 and approaches infinity.

In one or more embodiments, the semi-crystalline polymer of the PBM mayhave a density of from about 0.85 g/cm³ to about 0.92 g/cm³, or fromabout 0.86 g/cm³ to about 0.90 g/cm³, or from about 0.86 g/cm³ to about0.89 g/cm³ at room temperature and determined according to ASTM D-792.

In one or more embodiments, the semi-crystalline polymer of the PBM canhave a weight average molecular weight (Mw) of from about 5,000 to about500,000 g/mol, or from about 7,500 to about 300,000 g/mol, or from about10,000 to about 200,000 g/mol, or from about 25,000 to about 175,000g/mol.

Weight-average molecular weight, M_(w), molecular weight distribution(MWD) or M_(w)/M_(n) (also referred to as polydispersity index) whereM_(n) is the number-average molecular weight, and the branching index,g′(vis), are characterized using a High Temperature Size ExclusionChromatograph (SEC), equipped with a differential refractive indexdetector (DRI), an online light scattering detector (LS), and aviscometer. Experimental details not shown below, including how thedetectors are calibrated, are described in: T. Sun, P. Brant, R. R.Chance, and W. W. Graessley, Macromolecules, Volume 34, Number 19, pp.6812-6820, 2001. In one or more embodiments, the PBM can have apolydispersity index of from about 1.5 to about 6.

Solvent for the SEC experiment is prepared by dissolving 6 g ofbutylated hydroxy toluene as an antioxidant in 4 L of Aldrich reagentgrade 1,2,4 trichlorobenzene (TCB). The TCB mixture is then filteredthrough a 0.7 μm glass pre-filter and subsequently through a 0.1 μmTeflon filter. The TCB is then degassed with an online degasser beforeentering the SEC. Polymer solutions are prepared by placing the drypolymer in a glass container, adding the desired amount of TCB, thenheating the mixture at 160° C. with continuous agitation for about 2 hr.All quantities are measured gravimetrically. The TCB densities used toexpress the polymer concentration in mass/volume units are 1.463 g/mL atroom temperature and 1.324 g/mL at 135° C. The injection concentrationranges from 1.0 to 2.0 mg/mL, with lower concentrations being used forhigher molecular weight samples. Prior to running each sample the DRIdetector and the injector are purged. Flow rate in the apparatus is thenincreased to 0.5 mL/min, and the DRI was allowed to stabilize for 8-9 hrbefore injecting the first sample. The LS laser is turned on 1 to 1.5 hrbefore running samples.

The concentration, c, at each point in the chromatogram is calculatedfrom the baseline-subtracted DRI signal, I_(DRI), using the followingequation:c=K _(DRI) I _(DRI)/(dn/dc)where K_(DRI) is a constant determined by calibrating the DRI, and dn/dcis the same as described below for the LS analysis. Units on parametersthroughout this description of the SEC method are such thatconcentration is expressed in g/cm³, molecular weight is expressed inkg/mol, and intrinsic viscosity is expressed in dL/g.

The light scattering detector used is a Wyatt Technology HighTemperature mini-DAWN. The polymer molecular weight, M, at each point inthe chromatogram is determined by analyzing the LS output using the Zimmmodel for static light scattering (M. B. Huglin, Light Scattering fromPolymer Solutions, Academic Press, 1971):[K _(o) c/ΔR(θ,c)]=[1/MP(θ)]+2A ₂ cwhere ΔR(θ) is the measured excess Rayleigh scattering intensity atscattering angle θ, c is the polymer concentration determined from theDRI analysis, A₂ is the second virial coefficient, P(θ) is the formfactor for a monodisperse random coil (described in the abovereference), and K_(o) is the optical constant for the system:

$K_{o} = \frac{4\pi^{2}{n^{2}\left( {{{dn}/d}\; c} \right)}^{2}}{\lambda^{4}N_{A}}$in which N_(A) is the Avogadro's number, and dn/dc is the refractiveindex increment for the system. The refractive index, n=1.500 for TCB at135° C. and λ=690 nm. In addition, A₂=0.0015 and dn/dc=0.104 forethylene polymers, whereas A₂=0.0006 and dn/dc=0.104 for propylenepolymers.

The molecular weight averages are usually defined by considering thediscontinuous nature of the distribution in which the macromoleculesexist in discrete fractions i containing N_(i) molecules of molecularweight M_(i). The weight-average molecular weight, M_(w), is defined asthe sum of the products of the molecular weight M_(i) of each fractionmultiplied by its weight fraction w_(i):M _(w) ≡Σw _(i) M _(i)=(ΣN _(i) M _(i) ² /ΣN _(i) M _(i))since the weight fraction w_(i) is defined as the weight of molecules ofmolecular weight M_(i) divided by the total weight of all the moleculespresent:w _(i) =N _(i) M _(i) /ΣN _(i) M _(i)

The number-average molecular weight, M_(n), is defined as the sum of theproducts of the molecular weight M_(i) of each fraction multiplied byits mole fraction x_(i):M _(n) ≡Σx _(i) M _(i) =ΣN _(i) M _(i) /ΣN ₁since the mole fraction x_(i) is defined as N_(i) divided by the totalnumber of moleculesx _(i) =N _(i) /ΣN _(i)In the SEC, a high temperature Viscotek Corporation viscometer is used,which has four capillaries arranged in a Wheatstone Bridge configurationwith two pressure transducers. One transducer measures the totalpressure drop across the detector, and the other, positioned between thetwo sides of the bridge, measures a differential pressure. The specificviscosity, η_(s), for the solution flowing through the viscometer iscalculated from their outputs. The intrinsic viscosity, [η], at eachpoint in the chromatogram is calculated from the following equation:η_(s) =c[η]+0.3(c[η])²where c was determined from the DRI output.

The branching index (g′, also referred to as g′(vis)) is calculatedusing the output of the SEC-DRI-LS-VIS method as follows. The averageintrinsic viscosity, [η]_(avg), of the sample is calculated by:

$\lbrack\eta\rbrack_{avg} = \frac{\sum{c_{i}\lbrack\eta\rbrack}_{i}}{\sum c_{i}}$where the summations are over the chromatographic slices, i, between theintegration limits.

The branching index g′ is defined as:

$g^{\prime} = \frac{\lbrack\eta\rbrack_{avg}}{{kM}_{v}^{\alpha}}$where k=0.000579 and α=0.695 for ethylene polymers; k=0.0002288 andα=0.705 for propylene polymers; and k=0.00018 and α=0.7 for butenepolymers.

M_(v) is the viscosity-average molecular weight based on molecularweights determined by the LS analysis:M _(v)≡(Σc _(i) M _(i) ^(α/) Σc _(i))^(1/α)

In one or more embodiments, the semi-crystalline polymer of the PBM mayhave a viscosity (also referred to a Brookfield viscosity or meltviscosity), measured at 190° C. and determined according to ASTM D-3236from about 100 cP to about 500,000 cP, or from about 100 to about100,000 cP, or from about 100 to about 50,000 cP, or from about 100 toabout 25,000 cP, or from about 100 to about 15,000 cP, or from about 100to about 10,000 cP, or from about 100 to about 5,000 cP, or from about500 to about 15,000 cP, or from about 500 to about 10,000 cP, or fromabout 500 to about 5,000 cP, or from about 1,000 to about 10,000 cP,wherein 1 cP=1 mPa·sec.

The polymers that may be used in the injection molding compositionsdisclosed herein generally include any of the polymers formed asdisclosed in International Publication No. 2013/134038. The triadtacticity and tacticity index of a polymer may be controlled by thecatalyst, which influences the stereoregularity of propylene placement,the polymerization temperature, according to which stereoregularity canbe reduced by increasing the temperature, and by the type and amount ofa comonomer, which tends to reduce the length of crystalline propylenederived sequences.

Propylene-Based Elastomers

The polymer blends used to form the injection molding compositionsdescribed herein comprise one or more propylene-based elastomers(“PBEs”). The PBE comprises propylene and from about 5 to about 25 wt %of one or more comonomers selected from ethylene and/or C₄-C₁₂α-olefins. The α-olefin comonomer units may be derived from ethylene,butene, pentene, hexene, 4-methyl-1-pentene, octene, or decene. Inpreferred embodiments the α-olefin is ethylene. In some embodiments, thepropylene-based polymer composition consists essentially of propyleneand ethylene, or consists only of propylene and ethylene. Theembodiments described below are discussed with reference to ethylene asthe α-olefin comonomer, but the embodiments are equally applicable toother copolymers with other α-olefin comonomers. In this regard, thecopolymers may simply be referred to as propylene-based polymers withreference to ethylene as the α-olefin.

The PBE may include at least about 5 wt %, at least about 6 wt %, atleast about 7 wt %, or at least about 8 wt %, or at least about 9 wt %,or at least about 10 wt %, or at least about 12 wt % ethylene-derivedunits, where the percentage by weight is based upon the total weight ofthe propylene-derived and ethylene-derived units. The PBE may include upto about 30 wt %, or up to about 25 wt %, or up to about 22 wt %, or upto about 20 wt %, or up to about 19 wt %, or up to about 18 wt %, or upto about 17 wt % ethylene-derived units, where the percentage by weightis based upon the total weight of the propylene-derived andethylene-derived units. In some embodiments, the PBE may comprise fromabout 5 to about 25 wt % ethylene-derived units, or from about 7 wt % toabout 20 wt % ethylene, or from about 9 to about 18 wt %ethylene-derived units, where the percentage by weight is based upon thetotal weight of the propylene-derived and ethylene-derived units.

The PBE may include at least about 70 wt %, or at least about 75 wt %,or at least about 80 wt %, or at least about 81 wt % propylene-derivedunits, or at least about 82 wt %, or at least about 83 wt %propylene-derived units, where the percentage by weight is based uponthe total weight of the propylene-derived and α-olefin derived units.The PBE may include up to about 95 wt %, or up to about 94 wt %, or upto about 93 wt %, or up to about 92 wt %, or up to about 90 wt %, or upto about 88 wt % propylene-derived units, where the percentage by weightis based upon the total weight of the propylene-derived and α-olefinderived units.

The PBE can be characterized by a melting point (Tm), which can bedetermined by differential scanning calorimetry (DSC). Using the DSCtest method described herein, the melting point is the temperaturerecorded corresponding to the greatest heat absorption within the rangeof melting temperature of the sample. When a single melting peak isobserved, that peak is deemed to be the “melting point.” When multiplepeaks are observed (e.g., principal and secondary peaks), then themelting point is deemed to be the highest of those peaks. It is notedthat at the low-crystallinity end at which elastomers are commonlyfound, the melting point peak may be at a low temperature and berelatively flat, making it difficult to determine the precise peaklocation. A “peak” in this context is thus defined as a change in thegeneral slope of the DSC curve (heat flow versus temperature) frompositive to negative, forming a maximum without a shift in the baselinewhere the DSC curve is plotted so that an endothermic reaction would beshown with a positive peak.

The Tm of the PBE (as determined by DSC) may be less than about 115° C.,or less than about 110° C., or less than about 100° C., or less thanabout 95° C., or less than about 90° C. In some embodiments, the PBE mayhave two melting peaks as determined by DSC. In other embodiments, thePBE may have a single melting peak as determined by DSC.

The PBE may be characterized by its heat of fusion (Hf), as determinedby DSC. The PBE may have an Hf that is at least about 0.5 J/g, or atleast about 1.0 J/g, or at least about 1.5 J/g, or at least about 3.0J/g, or at least about 4.0 J/g, or at least about 5.0 J/g, or at leastabout 6.0 J/g, or at least about 7.0 J/g. The PBE may be characterizedby an Hf of less than about 75 J/g, or less than about 70 J/g, or lessthan about 60 J/g, or less than about 50 J/g, or less than about 45 J/g,or less than about 40 J/g, or less than about 35 J/g, or less than about30 J/g, or less than 25 J/g.

The DSC procedures for determining Tm and Hf of the PBE include thefollowing. The polymer is pressed at a temperature of from about 200° C.to about 230° C. in a heated press, and the resulting polymer sheet ishung, under ambient conditions, in the air to cool. About 6 to 10 mg ofthe polymer sheet is removed with a punch die. This 6 to 10 mg sample isannealed at room temperature for about 80 to 100 hours. At the end ofthis period, the sample is placed in a DSC (Perkin Elmer Pyris OneThermal Analysis System) and cooled to about −30° C. to about −50° C.and held for 10 minutes at that temperature. The sample is heated at 10°C./min to attain a final temperature of about 200° C. The sample is keptat 200° C. for 5 minutes. Then a second cool-heat cycle is performed.Events from both cycles are recorded. The thermal output is recorded asthe area under the melting peak of the sample, which typically occursbetween about 0° C. and about 200° C. It is measured in Joules and is ameasure of the Hf of the polymer.

Preferably, the PBE has crystalline regions interrupted bynon-crystalline regions. The non-crystalline regions can result fromregions of non-crystallizable propylene segments, the inclusion ofcomonomer units, or both. In one or more embodiments, the PBE has apropylene-derived crystallinity that is isotactic, syndiotactic, or acombination thereof. In a preferred embodiment, the PBE has isotacticsequences. The presence of isotactic sequences can be determined by NMRmeasurements showing two or more propylene derived units arrangedisotactically. Such isotactic sequences can, in some cases beinterrupted by propylene units that are not isotactically arranged or byother monomers that otherwise disturb the crystallinity derived from theisotactic sequences.

The PBE can have a triad tacticity of three propylene units (mmmtacticity), as measured by 13C NMR, of 75% or greater, 80% or greater,85% or greater, 90% or greater, 92% or greater, 95% or greater, or 97%or greater. In one or more embodiments, the triad tacticity may rangefrom about 75 to about 99%, or from about 80 to about 99%, or from about85 to about 99%, or from about 90 to about 99%, or from about 90 toabout 97%, or from about 80 to about 97%. Triad tacticity is determinedby the methods described in U.S. Pat. No. 7,232,871.

The PBE may have a tacticity index m/r ranging from a lower limit of 4or 6 to an upper limit of 8 or 10 or 12. The tacticity index, expressedherein as “m/r”, is determined by ¹³C nuclear magnetic resonance(“NMR”). The tacticity index, m/r, may be calculated as defined by H. N.Cheng in Vol. 17, MACROMOLECULES, pp. 1950-1955 (1984), incorporatedherein by reference. The designation “m” or “r” describes thestereochemistry of pairs of contiguous propylene groups, “m” referringto meso and “r” to racemic. An m/r ratio of 1.0 generally describes asyndiotactic polymer, and an m/r ratio of 2.0 describes an atacticmaterial. An isotactic material theoretically may have a ratioapproaching infinity, and many by-product atactic polymers havesufficient isotactic content to result in ratios of greater than 50.

The PBE may have a % crystallinity of from about 0.5% to about 40%, orfrom about 1% to about 30%, or from about 5% to about 25%, determinedaccording to DSC procedures.

The comonomer content and sequence distribution of the polymers can bemeasured using ¹³C nuclear magnetic resonance (NMR) by methods wellknown to those skilled in the art. Comonomer content of discretemolecular weight ranges can be measured using methods well known tothose skilled in the art, including Fourier Transform InfraredSpectroscopy (FTIR) in conjunction with samples by GPC, as described inWheeler and Willis, Applied Spectroscopy, 1993, Vol. 47, pp. 1128-1130.For a propylene ethylene copolymer containing greater than 75 wt %propylene, the comonomer content (ethylene content) of such a polymercan be measured as follows: A thin homogeneous film is pressed at atemperature of about 150° C. or greater, and mounted on a Perkin ElmerPE 1760 infrared spectrophotometer. A full spectrum of the sample from600 cm-1 to 4000 cm-1 is recorded and the monomer weight percent ofethylene can be calculated according to the following equation: Ethylenewt %=82.585−111.987X+30.045X2, where X is the ratio of the peak heightat 1155 cm-1 and peak height at either 722 cm-1 or 732 cm-1, whicheveris higher. For propylene ethylene copolymers having 75 wt % or lesspropylene content, the comonomer (ethylene) content can be measuredusing the procedure described in Wheeler and Willis. Reference is madeto U.S. Pat. No. 6,525,157 which contains more details on GPCmeasurements, the determination of ethylene content by NMR and the DSCmeasurements.

The PBE may have a density of from about 0.85 g/cm³ to about 0.92 g/cm³,or from about 0.86 g/cm³ to about 0.90 g/cm³, or from about 0.86 g/cm³to about 0.89 g/cm³ at room temperature, as measured per the ASTM D-792test method.

The PBE can have a melt index (MI) (ASTM D-1238, 2.16 kg @ 190° C.), ofless than or equal to about 100 g/10 min, or less than or equal to about50 g/10 min, or less than or equal to about 25 g/10 min, or less than orequal to about 10 g/10 min, or less than or equal to about 9.0 g/10 min,or less than or equal to about 8.0 g/10 min, or less than or equal toabout 7.0 g/10 min.

The PBE may have a melt flow rate (MFR), as measured according to ASTMD-1238 (2.16 kg weight @ 230° C.), greater than about 1 g/10 min, orgreater than about 2 g/10 min, or greater than about 5 g/10 min, orgreater than about 8 g/10 min, or greater than about 10 g/10 min. ThePBE may have an MFR less than about 1,000 g/10 min, or less than about750 g/10 min, or less than about 500 g/10 min, or less than about 400g/10 min, or less than about 300 g/10 min, or less than about 200 g/10min, or less than about 100 g/10 min, or less than about 75 g/10 min, orless than about 50 g/10 min. In some embodiments, the PBE may have anMFR from about 1 to about 100 g/10 min, or from about 2 to about 75 g/10min, or from about 5 to about 50 g/10 min.

The PBE may have a g′ index value of 0.95 or greater, or at least 0.97,or at least 0.99, wherein g′ is measured at the Mw of the polymer usingthe intrinsic viscosity of isotactic polypropylene as the baseline. Foruse herein, the g′ index is defined as:

$g^{\prime} = \frac{\eta_{b}}{\eta_{l}}$where ηb is the intrinsic viscosity of the polymer and ηl is theintrinsic viscosity of a linear polymer of the same viscosity-averagedmolecular weight (Mv) as the polymer. ηl=KMvα, K and α are measuredvalues for linear polymers and should be obtained on the same instrumentas the one used for the g′ index measurement.

The PBE may have a weight average molecular weight (Mw) of from about100,000 to about 300,000 g/mol, or from about 150,000 to about 250,000g/mol, or from about 150,000 to about 200,000 g/mol.

The PBE may have a number average molecular weight (Mn) of from about2,500 to about 2,500,000 g/mol, or from about 5,000 to about 500,000g/mol, or from about 10,000 to about 250,000 g/mol, or from about 25,000to about 200,000 g/mol.

The PBE may have a Z-average molecular weight (Mz) of from about 10,000to about 7,000,000 g/mol, or from about 50,000 to about 1,000,000 g/mol,or from about 80,000 to about 700,000 g/mol, or from about 100,000 toabout 500,000 g/mol.

The molecular weight distribution (MWD, equal to Mw/Mn) of the PBE maybe from about 1 to about 40, or from about 1 to about 15, or from about1.8 to about 5, or from about 1.8 to about 3.

Optionally, the propylene-based polymer compositions may also includeone or more dienes. In embodiments where the propylene-based polymercompositions comprises a diene, the diene may be present at from 0.05 wt% to about 6 wt % diene-derived units, or from about 0.1 wt % to about5.0 wt % diene-derived units, or from about 0.25 wt % to about 3.0 wt %diene-derived units, or from about 0.5 wt % to about 1.5 wt %diene-derived units, where the percentage by weight is based upon thetotal weight of the propylene-derived, alpha-olefin derived, anddiene-derived units.

In one or more embodiments, the PBE can optionally be grafted (i.e.,“functionalized”) using one or more grafting monomers. As used herein,the term “grafting” denotes covalent bonding of the grafting monomer toa polymer chain of the PBE. The grafting monomer can be or include atleast one ethylenically unsaturated carboxylic acid or acid derivative,such as an acid anhydride, ester, salt, amide, imide, acrylates or thelike. Illustrative monomers include but are not limited to acrylic acid,methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconicacid, mesaconic acid, maleic anhydride, 4-methylcyclohexene-1,2-dicarboxylic acid anhydride,bicyclo(2.2.2)octene-2,3-dicarboxylic acid anhydride,1,2,3,4,5,8,9,10-octahydronaphthalene-2,3-dicarboxylic acid anhydride,2-oxa-1,3-diketospiro(4.4)nonene, bicyclo(2.2.1)heptene-2,3-dicarboxylicacid anhydride, maleopimaric acid, tetrahydrophthalic anhydride,norbornene-2,3-dicarboxylic acid anhydride, nadic anhydride, methylnadic anhydride, himic anhydride, methyl himic anhydride, and5-methylbicyclo(2.2.1)heptene-2,3-dicarboxylic acid anhydride. Othersuitable grafting monomers include methyl acrylate and higher alkylacrylates, methyl methacrylate and higher alkyl methacrylates, acrylicacid, methacrylic acid, hydroxy-methyl methacrylate, hydroxyl-ethylmethacrylate and higher hydroxy-alkyl methacrylates and glycidylmethacrylate. Maleic anhydride is a preferred grafting monomer. In oneor more embodiments, the grafted PBE comprises from about 0.5 to about10 wt % ethylenically unsaturated carboxylic acid or acid derivative,more preferably from about 0.5 to about 6 wt %, more preferably fromabout 0.5 to about 3 wt %; in other embodiments from about 1 to about 6wt %, more preferably from about 1 to about 3 wt %. In a preferredembodiment, wherein the graft monomer is maleic anhydride, the maleicanhydride concentration in the grafted polymer is preferably in therange of about 1 to about 6 wt %, preferably at least about 0.5 wt %,and highly preferably about 1.5 wt %.

In an embodiment, the PBE is a dual-reactor blend of a first polymercomponent and a second polymer component. In some embodiments, thecomonomer content of the PBE can be adjusted by adjusting the comonomercontent of the first polymer component, adjusting the comonomer contentof second polymer component, and/or adjusting the ratio of the firstpolymer component to the second polymer component present in thepropylene-based polymer composition. In such embodiments, the firstpolymer component may comprise propylene and ethylene and have anethylene content of greater than 10 wt % ethylene, or greater than 12 wt% ethylene, or greater than 13 wt % ethylene, or greater than 14 wt %ethylene, or greater than 15 wt % ethylene, and an ethylene content thatis less than 20 wt % ethylene, or less than 19 wt % ethylene, or lessthan 18 wt % ethylene, or less than 17 wt % ethylene, or less than 16 wt% ethylene, where the percentage by weight is based upon the totalweight of the propylene-derived and ethylene derived units of the firstpolymer component. In such embodiments, the second polymer component maycomprise propylene and ethylene and have an ethylene content of greaterthan 2 wt % ethylene, or greater than 3 wt % ethylene, or greater than 4wt % ethylene, or greater than 5 wt % ethylene, or greater than 6 wt %ethylene, and an ethylene content that is less than 10 wt % ethylene, orless than 9.0 wt % ethylene, or less than 8 wt % ethylene, or less than7 wt % ethylene, or less than 6 wt % ethylene, or less than 5 wt %ethylene, where the percentage by weight is based upon the total weightof the propylene-derived and ethylene derived units of the secondpolymer component. In such embodiments, the PBE may comprise from 3 to25 wt % of the second polymer component, or from 5 to 20 wt % of thesecond polymer component, or from 7 to 18 wt % of the second polymercomponent, or from 10 to 15 wt % of the second polymer component, andfrom 75 to 97 wt % of the first polymer component, or from 80 to 95 wt %of the first polymer component, or from 82 to 93 wt % of the firstpolymer component, or from 85 to 90 wt % of the first polymer component,based on the weight of the PBE.

The PBE are preferably prepared using homogeneous conditions, such as acontinuous solution polymerization process in parallel reactors.Exemplary methods for the preparation of propylene-based polymer may befound in U.S. Pat. Nos. 6,881,800; 7,803,876; 8,013,069; and 8,026,323and PCT Publications WO 2011/087729; WO 2011/087730; and WO 2011/087731.The catalyst systems used for producing the PBE may comprise ametallocene compound, such as the catalyst used to prepare a PBMdescribed above.

Suitable PBEs for use in the present invention include some Vistamaxx™grades available from ExxonMobil Chemical, including Vistamaxx™ 6000series.

Polymer Blends

Polymer blends according to the present invention comprise at least onePBM and at least one PBE. The blend may comprise from about 45 or 55 or60 to about 70 or 80 or 85 wt % PBM based on the polymer blend. Theblend may comprise from about 15 or 25 or 35 to about 45 or 55 wt % PBEbased on the polymer blend. The polymer blends can be made bydry-blending a PBE with a PBM or by metering the components directlyinto an extruder at the desired ratio.

The polymer blends comprising at least one PBM and at least one PBE canadvantageously exhibit good flow properties and crystallizationcharacteristics. For example, the polymer blend may advantageouslyexhibit decreased mixer torque, which indicates a higher flow rate andimproved processability. For example, the polymer blend may exhibit amixer torque of less than 1,500 Nm, or less than 1,400 Nm, or less than1,300 Nm, or less than 1,200 Nm, or less than 1,100 Nm, or less than1,000 Nm. The mixer torque may be measured while mixing the polymerblend in a Brabender mixer for 10 minutes with a 50 rpm rotor rate at120° C.

In some embodiments, the polymer blends may also exhibit advantageouscrystallization characteristics. Higher crystallization rates and lowercrystallization times can lead to shorter manufacturing time when makinginjection molded articles. The difference in the onset crystallizationtemperature and the crystallization temperature of the polymer blend canbe used to indicate the crystallization rate of the polymer blend. Insome embodiments, the polymer blend exhibits a T_(onset)−T_(c) value ofless than 12° C., or less than 10° C., or less than 9° C. The T_(onset)and T_(c) may be measured as described in the Examples herein.

The polymer blends described herein are can be used as molten feedmaterial for injection molding apparatuses generally known in the art toconstruct a variety of plastic-based articles, e.g., packagingmaterials, automobile parts, furniture, stationery, and toiletries. Itshould be appreciated that the formulations of the present disclosure,while being well suited for use as injection molding articles, may alsofind utility in other applications as well.

In some embodiments, the polymer blends are used to form an injectionmolded article by a process that generally includes the steps ofadjusting a mold, filling a mold with a the molten polymer blend, andcooling the article constructed therefrom. For example, the moltenpolymer blend may be injected into the mold at an injection speed ofbetween 2 and 10 seconds. After injection, the material is packed orheld at a predetermined time and pressure to make the part dimensionallyand aesthetically correct. Typical time periods are from 5 to 25 secondsand pressures from 1,380 kPa to 10,400 kPa. The mold is cooled, forexample, between 10° C. and 70° C. The temperature will depend on thedesired gloss and appearance desired for the injection molded article.Typical cooling times are from 10 to 30 seconds, depending on article'sthickness. Finally, the mold is opened and the shaped article isejected.

The polymer blends useful for injection molded articles may furthercomprises one or more additive components in addition to the PBM and PBEcomponents described above. Various additives may be present to enhancea specific property or may be present as a result of processing of theindividual components. Additives which may be incorporated include, butare not limited to, fire retardants, antioxidants, plasticizers,pigments, vulcanizing or curative agents, vulcanizing or curativeaccelerators, cure retarders, processing aids, flame retardants,tackifying resins, flow improvers, and the like. Antiblocking agents,coloring agents, lubricants, mold release agents, nucleating agents,reinforcements, and fillers (including granular, fibrous, orpowder-like) may also be employed. Nucleating agents and fillers mayimprove the rigidity of the article.

EXAMPLES

Table 1 provides the Polymer Blend Modifiers (A to D) andPropylene-Based Elastomers (E to G) used to prepare the Polymer Blendsof the present invention. Table 2 provides the composition of eachPolymer Blend (i.e., by amount of Polymer Blend Modifier andPropylene-Based Elastomer). The PBMs and PBEs used in the examples wereprepared using a solution polymerization process in parallel reactorshaving a metallocene-based catalyst. The Blends of Table 2 were preparedby mixing the respective amount of modifier and elastomer components at50 rpm rotor rate for 10 minutes at 120° C. in a Brabender mixer. FIGS.1 to 3 report the processability parameters and crystallizationcharacteristics of a Polymer Blend having 15 to 95 wt % ofPropylene-Based Elastomer H and 5 to 85 wt % of Polymer Blend ModifiersA to D, respectively. While only the properties of Propylene-BasedElastomer H are reported in the Figures, it is expected that the otherPBEs of Table 1 would display similar processability and crystallizationproperties.

FIG. 1 shows processability parameters for polymer blends for use asinjection molding articles. The torque of the mixer was measured foreach of the Polymer Blends, as reported in Nm, during the 10 minutemixing process described above (50 rpm rotor rate at 120° C.) used toprepare the blends. In the examples of the invention, a Brabender mixerwas used as a torque rheometer to measure the difficulty of mixing therespective polymer blend. The torque of the mixer may be correlated tothe viscosity of the polymer blend, and hence processability of thepolymer blend. Low mixer torque generally indicates a higher flow andtherefore improved processability of the polymer blend. FIG. 1 showsthat mixer torque favorably decreases with the increase in the amount ofPBM in the Polymer Blend for PBM A through PBM D. Specifically, themixer torque for polymer blends having about 20 wt % PBM was about 800to about 1,500 Nm, for blends having about 45 wt % PBM was about 500 toabout 1,100 Nm, and for blends having about 85 wt % PBM was about 100 toabout 300 Nm. FIG. 1 shows that the lowest mixer torque was obtained forPBM A, consistent with Table 1 which indicates that PBM has the lowestMw of all the blend modifiers evaluated in the examples.

FIGS. 2 and 3 report crystallization characteristics of the PolymerBlends. These characteristics are related to the manufacturing time ofthe injection molding process, as the higher the crystallization rateand lower the crystallization time, the shorter the manufacturing timebecomes. FIGS. 2 and 3 show that PBMs B and C generally displayed lowerT_(onset)−T_(c) and t_(set) values than the other PBMs evaluated in theexamples.

FIG. 2 shows crystallization rate for polymer blends. Crystallizationrates were measured by Differential Scanning calorimeter (DSC). EachPolymer Blend was melted at 200° C. for 5 minutes and then cooled at therate of 10° C./minute. T_(onset)−T_(c) reported in FIG. 2 indicates therate of crystallization. The lower the T_(onset)−T_(c) value, the lesstime the respective Polymer Blend took to reach a maximumcrystallization rate. FIG. 2 shows that crystallization rate favorablyincreases with the increase in the amount of PBM in the Polymer Blend.Specifically, the T_(onset)−T_(c) value for polymer blends having about20 wt % PBM was about 10 to about 15° C., for blends having about 45 wt% PBM was about 6 to about 9° C., and for blends having about 85 wt %PBM was about 6 to about 7° C.

FIG. 3 shows crystallization time for polymer blends for use asinjection molding articles. Crystallization times were measured by DSC.Each Polymer Blend was cooled to 25° C. at the rate of 200° C./minuteafter holding at 200° C. for 5 minutes. The temperature was then held at25° C. constantly. The time for the Polymer Blend to crystallizecompletely was recorded as t_(set). FIG. 3 shows that crystallizationtime favorably decreases with the increase in the amount of PBM in thePolymer Blend after stabilizing, confirming the findings of FIG. 2.Specifically, the t_(set) value for polymer blends having about 20 wt %PBM was about 170 to about 210° C., for blends having about 45 wt % PBMwas about 130 to about 160° C., and for blends having about 85 wt % PBMwas about 120 to about 150° C.

TABLE 1 Estimated Melt Flow Ethylene Rate, Content, Mw, Mw/ PolymerBlend Components g/10 min wt % g/mol Mn Polymer Blend Modifier A >1,0004.01 27,600 2.36 Polymer Blend Modifier B >1,000 9.92 44,900 2.44Polymer Blend Modifier C >1,000 9.98 36,800 2.82 Polymer Blend ModifierD >1,000 6.57 29,300 2.19 Propylene-Based Elastomer E 5 9.19 257,9002.02 Propylene-Based Elastomer F 10 7.41 195,300 2.07 Propylene-BasedElastomer G 5 13.26 231,200 2.06 Propylene-Based Elastomer H 20 12.35136,500 2.02

TABLE 2 Polymer Polymer Blend Propylene-based Blend Modifier, wt %Elastomer, wt % 1 5 95 2 15 85 3 25 75 4 35 65 5 45 55 6 65 35 7 85 15

Certain embodiments and features have been described using a set ofnumerical upper limits and a set of numerical lower limits. It should beappreciated that ranges from any lower limit to any upper limit arecontemplated unless otherwise indicated. Certain lower limits, upperlimits, and ranges appear in one or more claims below. All numericalvalues are “about” or “approximately” the indicated value, and take intoaccount experimental error and variations that would be expected by aperson having ordinary skill in the art.

To the extent a term used in a claim is not defined above, it should begiven the broadest definition persons in the pertinent art have giventhat term as reflected in at least one printed publication or issuedpatent. Furthermore, all patents, test procedures, and other documentscited in this application are fully incorporated by reference to theextent such disclosure is not inconsistent with this application and forall jurisdictions in which such incorporation is permitted.

We claim:
 1. A composition comprising: a polymer blend of from about 45to about 85 wt % of a polymer blend modifier based on the polymer blendand from about 15 to about 55 wt % of a propylene-based elastomer basedon the polymer blend, wherein the polymer blend modifier comprises afirst propylene-based polymer, wherein the first propylene-based polymeris a homopolymer of propylene or a copolymer of propylene and ethyleneor a C₄ to C₁₀ alpha-olefin, and a second propylene-based polymer,wherein the second propylene-based polymer is a homopolymer of propyleneor a copolymer of propylene and ethylene or a C₄ to C₁₀ alpha-olefin,wherein the second propylene-based polymer is different than the firstpropylene-based polymer; and wherein the polymer blend modifier has aweight average molecular weight of about 10,000 to about 100,000 g/moleand wherein the propylene-based elastomer has a weight average molecularweight of about 100,000 to about 300,000 g/mole.
 2. The composition ofclaim 1, wherein the mixer torque for the polymer blend is reduced byabout 1 to about 2% for every 1 wt % increase in the amount of thepolymer blend modifier in the polymer blend.
 3. The composition of claim1, wherein the polymer blend modifier has a melt flow rate, as measuredaccording to ASTM D-1238 (2.16 kg at 230° C.), of greater than about1,000 g/10 min to less than about 10,000 g/10 min and wherein thepropylene-based elastomer has a melt flow rate, as measured according toASTM D-1238 (2.16 kg at 230° C.), of less than about 100 g/10 min. 4.The composition of claim 1, wherein the propylene-based elastomercomprises propylene and from about 5 to about 25 wt % units derived fromone or more C₂ or C₄-C₁₂ alpha-olefins and has a triad tacticity greaterthan about 90% and a heat of fusion less than about 75 J/g.
 5. Thecomposition of claim 1, wherein the polymer blend modifier is a dualreactor blend.
 6. The composition of claim 1, wherein the polymer blendmodifier is a solution blend.
 7. The composition of claim 1, wherein thefirst propylene-based polymer of the polymer blend modifier comprises acopolymer of propylene and ethylene, and the second propylene-basedpolymer of the polymer blend modifier comprises a copolymer of propyleneand ethylene.
 8. The composition of claim 1, wherein the firstpropylene-based polymer of the polymer blend modifier and the secondpropylene-based propylene polymer of the polymer blend modifier have adifference in heat of fusion of at least 10 J/g.
 9. The composition ofclaim 1, wherein the propylene-based elastomer is a reactor blend of afirst polymer component and a second polymer component.
 10. Thecomposition of claim 9, wherein the first polymer component comprisespropylene and ethylene and has an ethylene content in the range of about10 wt % to about 20 wt % based on the weight of the first polymercomponent.
 11. The composition of claim 9, wherein the second polymercomponent comprises propylene and ethylene and has an ethylene contentin the range of about 2 wt % to about 10 wt %, based on the weight ofthe second polymer component.
 12. The composition of claim 9, whereinthe propylene-based elastomer comprises from 3 to 25 wt % of the secondpolymer component, based on the weight of the propylene-based elastomer.13. The composition of claim 1, wherein the polymer blend modifier has apolydispersity index of about 1.5 to about
 6. 14. The composition ofclaim 1, wherein the propylene-based elastomer has a polydispersityindex of about 1.8 to about
 3. 15. An injection molded articlecomprising the composition of claim
 1. 16. A process comprising: moldinga composition comprising (a) from about 45 to about 85 wt % of a polymerblend modifier based on the composition; and (b) from about 15 to about55 wt % of a propylene-based elastomer based on the composition, whereinthe polymer blend modifier comprises a first propylene-based polymer,wherein the first propylene-based polymer is a homopolymer of propyleneor a copolymer of propylene and ethylene or a C₄ to C₁₀ alpha-olefin,and a second propylene-based polymer, wherein the second propylene-basedpolymer is a homopolymer of propylene or a copolymer of propylene andethylene or a C₄ to C₁₀ alpha-olefin, wherein the second propylene-basedpolymer is different than the first propylene-based polymer; and whereinthe polymer blend modifier has a weight average molecular weight ofabout 10,000 to about 100,000 g/mole and wherein the propylene-basedelastomer has a weight average molecular weight of about 100,000 toabout 300,000 g/mole by the use of an injection molding machine.
 17. Theprocess of claim 16, wherein the polymer blend modifier is dry blendedwith the propylene-based elastomer to form the composition.
 18. Theprocess of claim 16, wherein the polymer blend has a mixer torque ofless than 1,500 Nm.
 19. The process of claim 16, wherein the polymerblend exhibits a T_(onset)−T_(c) value of less than 12° C.
 20. Theprocess of claim 16, further comprising holding the polymer blend at apressure from 1,380 kPa to 10,400 kPa for from 5 to 25 seconds.